Keying system



Oct. 13, 1953 T. H. CHAMBERS KEYING SYSTEM Filed Aug. 9, 1945 gwovrvfov TORRENCE H. CHAMBERS NW u Patented Oct. 13, l953 N l TED STATES PATENT 'OFFI (IE .KEYING SYSTEM Terrence H. Chambers, Washington, D. 0.

Application August 9, 1945, Serial No. 609,910

(Granted under Title as u. s. (1952-).

Glahns.

sec26 This invention relates to a keying system for a pulsed radio frequency transmitter and, more particularly, to a keyer suitable for use in connection with radio obstacle-detecting systems.

An object of this invention is to provide a mean of producing a series of short pulses of radio frequency energy in which the individual pulses are differently spaced.

Another object of the invention is to provide a means of producing at predetermined intervals short trains of pulses of radio frequency energy wherein the individual pulses may be spaced irregularly.

A better understanding of the objects, features, and advantages of the present invention will be obtained from the following. detailed description of a practical embodiment thereof when read in conjunction with the accompanying drawing whose single figure shows a schematic diagram of the electrical circuit employed.

In accordance with the present invention the random keying system comprises plurality of energy storage condensers adapted to be discharged separately through a relay which momentarily breaks the connection between a high- 1y negative voltage source and the grids of a pair of transmitting tubes constituting a selfpulsing oscillator. The action of the relay is rapid enough to prevent the production of a secand pulse of radio frequency energy beforethe above-mentioned connection to the negative biasing potential is restored. The individual condensers are discharged by gas-filled tubes whose control grids are maintained at high negative potentials until the generation of a train of. pulses is desired. At that time the grid return leads are shorted to ground. By providing R-C time-constant circuits betweenthe grids and the ground-ends of the grid return leadsofall the gas-filled tubes except-the first, a time delay is obtained in the firing of those tubes. 5 The approximate delay is determined by the setting of variableresistors located in these time-constant circuits and may therefore be adjusted to give any desired spacing between successive discharges and consequently between successivepulses. A second relay is provided operated by a mechanical timing switch for the purpose of connecting the discharged capacitors and the grid return leads to proper potential sources in preparation for a new train of pulses; A repetitionrof the train of pulses is brought about by removing the connections to the charging and. biasing potentials and subsequently grounding the grid return leads;

Referring now in detail to the single figure of the drawing, the tubes l0, l0 thereshown constitute an ultra-high-radio-frequency oscillator of the self-pulsing type whose grids l2, I2 are normally held at a very negative voltage with respect to their cathode I3, l3 as a result of their connection through stationary contact I4 and the movable blade of relay [-5, and via line IE to a suitable source of negative voltage ("C) which is large compared to the normal cut-off potential of the tubes l0, Hi. When the contact M is broken by the operation of the relay [5, the condenser H discharges through the resistance path formed by resistors Ill and 19. As soon as the condenser I! has discharged'to' a point just beyond the cut-off biasing voltage for the tubes l0, ill, the oscillator becomes operative and the grids thereof are driven positive during each cycle of the radio frequency oscillation thereby causing grid current to flow. As a result of this flow of grid current, the tubes H1, 10 become more negatively biased and in a relatively short time the plate current pulses can no longer supply sufficient power to the grid circuit to maintain the oscillations. By making the time required for the charge on the condensers i1 and 20 to discharge through the resistance path including resistors i8, i9 and 2| relatively long, the connection of the grids l2,-

l2 to the negative voltage source (C) is reestablished by the closing of the relay I 5, to

effect circuit connection of its movable blade with contact 14, before the circuit can break into oscillation again. In that way a pulse genera tor circuit is provided which will generate a single pulse of radio frequency energy each time the relay l5 opens the circuit between the con-' tact I4 and the cooperating movable blade of the relay.

Means are provided for operating the relay I5 and preferably comprise a plurality of thyratrons of which the figure shows three byway of example and indicated as gas tubes or gas triodes 22, 23 and 24. their respective cathodes 25 tied together and they are connected through the coil of the relay iii to a point at ground potential. The grid 26 of tube 22 is connected through the lead 21, the movable blade of relay 38, and stationary contact 28 to a source of negative voltage (C) sufficient to prevent the tube 22 from firing even when the condenser 29 is fully chargedv The charging circuitof condenser 29 includes a current-limiting resistor 30 and a connection by way of the movable blade of relay 38 and sta- These thyratrons have tionary contact 3| to a source of voltage indicated as (+13). The capacitance of the condenser 29 is chosen so as to provide for a sumcient storage of energy to insure proper operation of the relay l when the condenser 29 is discharged by the tube 22 through the coil of the relay IS. The current-limiting resistor 30 should be as large as can be used and still insure that the condenser 29 will be properly charged during the interval between the expected trains of pulses.

A time-constant circuit including variable resistor 32 and condenser 33 is provided for holding the grid 34 of tube 23 biased beyond cut-01f for a predetermined interval of time after the grid return lead has been disconnected from the source of biasing potential (-C) and connected to ground through the movable blade 01' relay 38 and stationary contact 28 by the operation of this relay. Adjustment of the variable resistor 32 will alter the time of firing of the tube 23. The choice of maximum R-C product will determine the extent of possible delay in firing after the grounding of the return lead 21. An energy storage condenser 35 and ourrent-limiting resistor 36 are provided for the tube 23, the respective values of which being identical with those of condenser 29 and resistor 30 used with tube 22 and so chosen because the charging time available is preferably the same for all the storage condensers employed.

It will be obvious that any number of additional thyratrons can be provided each with a circuit similar to that of tube 23 of which the stage including gas tube 24 is illustrative. If the R-C time constants used in the grid circuits are made so that they are adjustable to a number of different values, the times of delay in the discharging of the plurality of storage condensers may be chosen arbitrarily in order to obtain an irregularly spaced group of discharges which will bring about an irregularly spaced group of ultra-highradio-frequency pulses.

A cam-operated timing switch 31 is provided to energize the coil of the relay 38 to actuate the latter intermittently to a source of voltage (+13) thereby energizing the coil of the relay and simultaneously actuating the movable blades thereof to open the contacts 28 and 3| thereby to discontinue the charging of the grid and plate ciruit condensers of the thyratrons and begin the cycle of discharge. Cam 39 for actuating the mechanical timing switch 3'! may be driven by a suitable motor (not shown) and carries on its periphery a series of lugs 40 which may be either regularly or irregularly spaced thereon, as desired. Manifestly, any desired spacing may be employed for the lugs but in the illustrated embodiment the lugs 40 are shown as being unequally positioned.

Thus, there has been described a means 01 keying a self-pulsing oscillator in such a way that it emits discrete pulse trains each of which contains a perdetermined number of pulses appearing with irregular time spacing and repeatable after predetermined intervals of time. The substitution of a hand-operated key or switch for the cam-operated switch 31 obviously will enable the operator to produce trains of spaced pulses in sequential, irregularly-spaced distribution of the same character as those produced by the preferred embodiment above described except that the time spacing intervals between successive trains of pulses can be made either regular or irregular, as desired, so long as sufllcient spacing is provided between successive trains of pulses to allow the storage condensers above described to become fully charged.

It will be obvious to those skilled in the art that various changes and modifications may be made in the embodiment of the invention without departing from the spirit thereof, and it is therefore to be distinctly understood that no limitations are intended other than are imposed by the scope of the appended claims and limited by the prior art.

The invention described herein may be manufactured and used by or for the Government of the United States of America for govenmental purposes without the payment of any royalities thereon or therefor.

What is claimed is:

1. A keying system for a pulsed radio frequency transmitter comprising a relay operating a switch for alternately rendering said radio frequency transmitter operative and inoperative,

a plurality of condensers each connected througha current-limiting resistor to a source of charging potential, a plurality of gas-filled discharge tubes for discharging said condensers through said relay at irregularly spaced times, means applying negative biasing voltage to said gasfilled discharge tubes until said discharging action is desired, means for removing said negative bias from said gas-filled discharge tubes in sequence, a second relay, and timer means for controlling the operation of said second relay to make and break the electrical circuit connec tions between said gas filled discharge tubes and said charging potential.

2. A keying circuit for controlling the operation of an oscillation generator in a high-frequency signalling system, said oscillator employing vacuum tubes each having an anode, a cathode and a control grid, said generator being normally blocked by a high negative biasing potential, applied to the grids of said tubes, means for temporarily removing said negative biasing voltage from the grid of said oscillator tubes, a plurality of gas-filled tubes connected in parallel each having a cathode, a plate and a control grid, means for energizing said plates, electrical energy storage means connected to the individual plates, the grids of said gas tubes being held at high negative potential until generation of a pulse train, relay means grounding the grids of said gas tubes during generation of a pulse train, resistance-capacitance time-constant circuits each with a variable resistor associated with all gas tubes except the first for providing a time delay in firing of all gas tubes except the first, said variable resistors serving to provide variable spacing of the pulses in each train, switch means for connecting the grid returns of said gas tubes and the discharged condensers to the high negative bias voltage and the high positive plate voltage sources respectively, cam mechanism for actuating said switch means, the repetition and spacing of successive groups of pulse trains being effected by removal of the charging and biasing potentials from said gas tubes and the simultaneous grounding of their grid return leads by operation of said cam actuated switch.

3. A keying system for a pulsed radio frequency transmitter including an oscillator having an electron tube with anode, cathode and control grid electrodes comprising, a relay having a coil and contact members responsive to energization of the coil, a biasing source for the electron tube providing through the relay contact members greater than cutoff bias therefor, a plurality of electrical energy storage condensers, a plurality of gas-filled discharge tubes connected to the condensers and to the coil of the relay operative upon ionization thereof to discharge each condenser through the coil of the relay to remove the greater than cut-ofi bias on the electron tube, and means sequentially ionizing the discharge tubes at a random sequence recurrence rate.

4. A keying system for a pulsed radio frequency transmitter having an electron tube with anode, cathode and grid electrodes comprising. means for changing the biasing potential applied to the grid of the electron tube, said means including a source of cut-01f biasing potential and a relay actuated switch for connecting or disconnecting the electron tube grid to the source of biasing potential, a resistor-capacitor network connected to the electron tube grid determining the duration of each transmitter pulse, a plurality of gas-filled discharge tubes having anode. cathode and grid electrodes, said gas-filled discharge tubes connected to the relay operative to discharge energy through said relay at sequential time instants, secondary resistor-capacitor circuits having different time constants controlling the discharge of said gas-filled discharge tubes, said secondary resistor-capacitor circuits being connected individually to the grids of said gas-filled discharge tubes, and timer means for initiating the sequential discharges oi. said secondary resistor-capacitor circuits.

5. In a keying circuit in combination, electrical energy storage condensers, and means spacing the times of discharge of said electrical energy storage condensers comprising a plurality of gas-filled discharge tubes of the thyratron type having anode, cathode and grid electrodes, said gas-filled discharge tubes connected individually one to each electrical energy storage condenser to discharge said condensers upon ionization thereof, means applying a blocking bias to the grids of said tubes, and means sequentially removing the blocking bias from said tubes including resistor-capacitor time constant networks disposed between the grids and the blocking bias means of certain of said tubes.

TORRENCE H. CHAMBERS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,873,786 Ranger Aug. 23, 1932 1,913,588 Francis June 13, 1933 1,914,407 Demarest June 20, 1933 1,984,105 Zetzmann Dec. 11, 1934 2,076,335 Dallenbach 1 Apr. 6, 1937 2,134,562 Kimmich Oct. 25, 1938 2,391,894 Gorham et a1 Jan. 1, 1946 2,407,272 Hart Sept. 10, 1946 2,416,327 Labin Feb. 25, 1947 OTHER REFERENCES "Radar System Fundamentals." Navshlns 900.- 017, Navy Department, April 1944. 

